Provided are methods and compositions for identifying candidate agents for treatment of obesity, liver disease, and/or diabetes. Such methods include, e.g., contacting a mammalian cell or cell population with a test agent, and measuring an expression level and/or activity level of ClpP in the mammalian cell or in cells of the cell population. Also provided are methods and compositions for treating an individual (e.g., one who is obese and/or has diabetes). Treatment methods include administering an inhibitor of ClpP to the individual (e.g., to prevent or reduce weight gain, to increase insulin sensitivity, and/or to increase glucose tolerance).